An electrochromic device is capable of varying its light transmission in response to the application of an electric field, and can be used for applications such as windows, rear-view mirrors, etc. When the electrochromic device is used as a rear-view mirror, it can control the flow of light reflected toward the driver so as to prevent the driver from being blinded by bright lights from a following car.
As shown in FIGS. 1 and 2, a conventional electrochromic device includes a front glass substrate 11, a rear glass substrate 13, a front transparent electrode layer 17 formed on a rear surface of the front glass substrate 11, a rear transparent electrode layer 15 formed on a front surface of the rear glass substrate 13, an electrochromic laminate 16 disposed between the front and rear transparent electrode layers 17, 15, and a looped adhesive layer 14 surrounding the electrochromic laminate 16 and disposed between the front and rear transparent electrode layers 17, 15 to thereby bond the front glass substrate 11 to the rear glass substrate 13. The electrochromic laminate 16 includes an active layer (not shown) made of an electrochromic material, an ion storage layer (not shown), and an electrolyte layer (not shown) sandwiched between the active layer and the ion storage layer. The transparency of the electrochromic laminate 16 can be varied by applying an electric field between the front and rear transparent electrode layers 17, 15.
To apply an electric field between the front and rear transparent electrode layers 17, 15, the front and rear glass substrates 11, 13 should overlap in such a way as to partially expose the front and rear transparent electrode layers 17, 15, as shown in FIG. 1. The exposed portions of the front and rear transparent electrode layers 17, 15 may be protected by two protecting members 12. However, as the frame need be constructed to cover the protecting members 12 when the electrochromic device is assembled to a frame for a window or a rear-view mirror so that the electrochromic device can be firmly retained in the frame, the effective surface area of the conventional electrochromic device is undesirably reduced.